Viltrox C-AF 2x Magnification Teleconverter Extender Auto Focus Mount Lens for Canon EOS Ef Lens 5d Ii 7d 6d T5i T4i T3i 5d Ii 7d 6d T5i T4i T3i 1200d 760d 750d Viltrox C-AF 2X TELEPLUS can make the focal length of all the for Canon EF lens increased to 2 times as respectively. C-AF 2X specially use for 100mm or more fixed focal length lens, but not recommend for use in less than 60mm of short-focus lens. The auto-focus function of the original camera lens can be used perfectly, and don't change the EXIF information. Mount Type: for Canon EF-Mount lens Depth of field: Half of the original lens Constitution of the lens: 7 glasses,4 groups